1. Field of the Invention
The present invention relates to a frequency converter, and more particularly to a fan control device for a frequency converter that installs heat dissipating fans according to the internal mechanical design and the heat dissipating requirements of the frequency converter and uses the internal temperature change to control the speed of the fans of the frequency converter.
2. Description of Prior Art
In general, present heat dissipating designs used in a frequency converter system adopt heat dissipating fans to achieve a heat dissipating function, and the positions for installing the heat dissipating fans and the operation control of the fans determine the heat dissipating effect. Thus, good layout design and operation control will enhance the operating performance of the frequency converter.
The prior art heat dissipating devices applied to a high-power frequency converter system (over 200 HP) install AC fans. Although it is easier to use AC fans, yet the AC fans can be installed and fixed in a specific direction only and thus constituting a limitation to the mechanical design of the frequency converter system. In other words, the direction and position for installing the AC fans cannot be changed flexibly according to the mechanical design and the heat dissipating requirements. Further, the operation of AC fans requires a fixed voltage supply, but a constant operating speed is usually required. The AC fans cannot be operated at different speeds according to the actual temperature change, and thus these AC fans have a poor speed control capability. If it is necessary to control the speed of an AC fan, a complicated drive circuit will be needed. As a result, the production cost will be increased. In addition, the AC fan is driven by a fixed voltage to maintain a constant speed for its operation even when the frequency converter is at an idle state, and thus wasting unnecessary power consumption at an idle state as well as creating a noise problem.